1. Field of the invention
The present invention relates to imaging systems with printers and optional support devices therefor, and more particularly relates to printers, such as laser printers, having options (e.g., paper handling devices) which contain electronic intelligence for carrying out local option functions commanded by the printer.
2. Description of the related art
Imaging, or printing, systems typically include a base printer, which places marks (i.e., prints) on print receiving media (e.g., paper) and medium (e.g., paper) handling options, or devices, that perform various functions such as, for example, providing for multiple paper input sources, multiple paper output destinations, duplexing (i.e., 2-sided printing on the media), stacking and collating. Such printer systems include a base printer having a printer controller, or print engine, including a microprocessor and associated electronic units. Control of the printer and paper-handling features of such a simple print system are handled by the print engine. As printer systems add a small number of optional devices, such as additional input sources, the control of the additional devices is provided by the print engine. For example, the printer option might have electronics to control portions of its own mechanism in which case the print engine controls the mechanism of the optional device directly through discrete electrical signals or via a unidirectional serial transmission, i.e., communications from the print engine to the device only. The printer engine controls the optional device directly with dedicated electrical signal lines used to turn a device motor on, turn the motor off, activate a device clutch, etc.
As printer systems become more complex, it is impractical for the print engine to directly control the entire printer system's electro-mechanical mechanism. Thus, printer systems have migrated to an architecture in which the printer acts as a "master" of "smart" or intelligent optional devices. Each intelligent optional device typically contains a microprocessor and associated electronics and microcode, to control its own electro-mechanical mechanism. The print engine, in turn, controls or manages the function of the optional devices as black boxes via a communications interface.
Various printers operate over a wide range of print speeds, thereby offering different levels of performance. The print media must be fed through the printer system at a rate, known as a process speed, which relates to the print speed of the printer.
It is known to design smart paper handling options such that a single option can accommodate any printer in a family of printers, each having different print speeds. Thus, a single smart paper handling option must be capable of feeding print media at various process speeds, each of which relates to the print speed of a respective printer in a family of printers.
For existing smart paper handling options, it is known to design the smart paper handling option to be capable of feeding print media at only a few possible process speeds, each of which relates to the print speed of a particular printer. A printer identifies itself, along with its process speed, to the smart paper handling option through a communication link and the smart paper handling option then selects which of its preprogrammed process speeds corresponds to the printer that is presently attached. The smart paper handling option includes a print medium transport assembly which includes a controller, motor and sensors which are capable of transporting a print medium at only one of the preprogrammed process speeds. A problem is that such smart paper handling options are not adaptable to printers having print speeds which do not correspond to any of the finite set of available process speeds within the smart paper handling option. Thus, in order to accommodate a new printer having a new print speed, an existing smart paper handling option must be removed and reworked or may even have to be scrapped and replaced with a newly designed smart paper handling options supporting the new printer's process speed(s). Each new family of printers having a new set of print engine speeds requires the rework of existing smart paper handling options or requires replacement with entirely new smart paper handling options in order to feed the print media at the correct speeds.
Existing smart paper handling options include look-up tables which provide control equations with fixed parameters corresponding to each of a finite number of discrete printer speeds. The control equations are used to drive the print medium transport assembly.
What is needed in the art is a method of relating in real-time a smart paper handling option process speed with any of a continuous range of print engine speeds, rather than with just a finite set of discrete print engine speeds.